It doesn't happen often, but once or twice every decade a motion picture comes along that redefines its genre. "Identity," complexly written by Michael Cooney and stunningly crafted by director James Mangold (1999's "Girl, Interrupted"), may just invigorate to life slasher movies the same way that 1999's "The Sixth Sense" jump-started supernatural thrillers. Similarities between M. Night Shyamalan's monster hit and this film are superficial, at best, but they do share a willingness to offer up something startlingly fresh, thoroughly unpredictable, genuinely creepy, and unshakably thought-provoking. By the time "Identity" reaches its heart-stopping final twist of a scene (never mind the corkscrew zinger that comes fifteen minutes earlier), it is safe to say not a single audience member will be able to pinpoint another film quite like the one that he or she has just encountered.

Taking a page from Agatha Christie's classic, "Ten Little Indians," "Identity" places ten strangers within a secluded and ominous setting, and then proceeds to methodically bump them off at the hands of a mystery killer. It's a dark and stormy night in the Nevada desert. With the roads flooded, seemingly unrelated travelers are forced to check in at an out-of-the-way motel. The victims/suspects include a limousine driver (John Cusack) chauffeuring has-been television actress Caroline Suzanne (Rebecca De Mornay); a down-on-their-luck family consisting of a sincere stepfather (John C. McGinley), a critically injured mother (Leila Kenzle), and a mute son (Bret Loehr); an argumentative newlywed couple (Clea DuVall, William Lee Scott); a just-retired prostitute (Amanda Peet) headed for her Florida hometown to start over; and a police officer (Ray Liotta) transferring a convict (Jake Busey) across the state. As these people start getting killed off in what increasingly seems like a systematic fashion, they discover that they are all somehow linked. But who is the cold-blooded murderer? And what is their motive?

Reading the premise, you may think you've got it all figured out, or sigh with the feeling that you have seen such a tried-and-true formula played out countless times before. Think again. "Identity" may be a horror movie with a body count for its first hour, albeit a particularly chilling and faultlessly orchestrated one, but then it blindsides with the sort of plot revelations that turn everything that has come before and everything that follows on its head. It is utterly incalculable, even as you may scold yourself for not picking up on all the carefully placed clues along the way. More importantly, though, this novel twist does not pop up for the sole reason of fooling the viewer, but has a real purpose for being. It metamorphoses "Identity" from what could have been just a high-gloss, unusually well-cast slasher movie into something markedly deeper, substantially richer, and far more existential in nature. To say any more about the climactic truths uncovered would be blasphemy directed toward those who have not had the pleasure of experiencing this compact, 90-minute gem.

Director James Mangold delights in the first two acts in toying with the typical slasher movie conventions, all the while cooking up something far closer in atmosphere and style to Alfred Hitchcock than, say, "Friday the 13th." The killings, although occasionally bloody, appear more often after the fact than during the act, but it is in his classic-style setups that Mangold really comes into his own. He is aided by the sumptuously moody and detailed cinematography by Phedon Papamichael (2002's "Moonlight Mile"), superbly putting shadows and pouring rain to expert use, and the tight, meticulously woven editing by David Brenner (2001's "Kate and Leopold").

At around the 65-minute mark, Mangold suddenly pulls the genre safety net out from under the viewers, but in a good way. Yes, it forces us to look at everything differently, but it also strengthens rather than cheapens what has already come. And, best of all, it adds levels of poignancy and depth to the proceedings, just as the second twistin the final minutesreturns the movie with a bang to its veritably scary and disturbing roots.

The cast, filled from all sides by real talent, fit right in. John Cusack (2002's "Max") is so perfect in his sort of laid-back, everyman kind of roles, and his Ed makes for an enthralling protagonist. As former prostitute Paris, who just wants to get to Florida and start an orchard, Amanda Peet (2002's "Changing Lanes") matches Cusack scene for scene, developing her role far more than what is expected of a female heroine, usually on hand to just run and scream (although she does these quite well too). As the questionably off-kilter motel clerk, John Hawkes (2000's "The Perfect Storm") brings an unforced, distinguishable energy to his scenes. Everyone elseespecially the wonderful Clea DuVall (2002's "Thirteen Conversations About One Thing"), the always interesting Ray Liotta (2001's "Heartbreakers"), and bright young newcomer Bret Loehrare standouts in purposefully archetypal roles.

Ultimately, how general audiences perceive the third act will make or break "Identity" at the box office. It does not offer simple answers, does not always follow through with what is expected of a spooky whodunit, and will be rendered useless for those who don't pay close attention, opting to make unnecessary bathroom runs and cell phone calls as the movie is still playing itself out. For those who are tired of the "same old thing," however, "Identity" makes for a surprisingly challenging and rewarding motion picture experience, as ruminating and hard to forget as it is thrillingly wicked and suspenseful. Move over, "Psycho" and "Rosemary's Baby""Identity" has every last thing it takes to achieve classic modern horror film status.